toolhead: Commands should still pause even when sync_print_time

If commands are slowly fed to the printer it could cause the number of
queued commands to grow without bound.  Be sure to pause the incoming
command stream even if the lookahead queue is empty.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/toolhead.py

@@ -316,7 +316,6 @@ class ToolHead:
                     self.print_stall += 1
                 self.idle_flush_print_time = 0.
             self.reactor.update_timer(self.flush_timer, eventtime + 0.100)
-            return
         # Check if there are lots of queued moves and stall if so
         while 1:
             est_print_time = self.mcu.estimated_print_time(eventtime)
@@ -328,7 +327,9 @@ class ToolHead:
                 self.need_check_stall = self.reactor.NEVER
                 return
             eventtime = self.reactor.pause(eventtime + min(1., stall_time))
-        self.need_check_stall = est_print_time + self.buffer_time_high + 0.100
+        if not self.sync_print_time:
+            self.need_check_stall = (est_print_time + self.buffer_time_high
+                                     + 0.100)
     def _flush_handler(self, eventtime):
         try:
             print_time = self.print_time